Oil dispensing apparatus

ABSTRACT

Apparatus for lubricating the heated fuser roll in a heated pressure xerographic fusing system. The apparatus includes an applicator roll for providing a film of oil to a wick assembly having a main wick contacting the fuser roll and an auxilliary wick with one end and main wick contacting the applicator roll and the other end the bottom of an oil pan supply to dispense sufficient oil when the applicator roll is inoperative.

United States Patent 91 Thettu OIL DISPENSING APPARATUS [75] Inventor: Raghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: July 20, 1971 [21] Appl. No.: 164,369

[52] US. Cl. ..1l8/266,101/l32.5, 118/60,

118/264 [51] Int. Cl ..B05c 11/00 [58] Field of Search ..l18/265, 266, 267, 243, 203, 118/60, 264, DIG. 23; 101/147, 148, 132.5,

[56] References Cited UNITED STATES PATENTS 1,276,408 8/1918 Peterson ..1 18/243 51 Feb. 27, 1973 274,804 3/1883 McVoy ..1 18/265 2,937,390 5/1960 Bolton et a1. ..l5/3 3,194,155 7/1965 Davis, Jr ..l01/366 2,754,752 7/1956 Robinson et al ...101/132.5 2,781,021 2/1957 Schmitz ..1 18/264 Primary Examiner-Mervin Stein Assistant ExaminerLeo Millstein Attorney-James J. Ralabate et al.

[5 7] ABSTRACT Apparatus for lubricating the heated fuser roll in a heated pressure xerographic fusing system. The apparatus includes an applicator roll for providing a film of oil to a wick assembly having a main wick contacting the fuser roll and an auxilliary wick with one end and main wick contacting the applicator roll and the other end the bottom of an oil pan supply to dispense sufficient oil when the applicator roll is inoperative.

5 Claims, 4 Drawing Figures PATENTED FEB 2 71973 SHEET 1 OF 3 INVENTOR. RAGHULINGA R. THETTU ATTORNEY PATENTED FEB 2 7 I973 SHEET 2 OF 3' FIG. 2

This application relates to fusing systems and in particular to an improved lubricating apparatus for removing toner particles from the fuser roll of a heated pressure fusing system.

In the practice of xerography as described in U.S. Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic surface is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where the light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image can then be developed by contacting it with a finely divided electrostatically attractable material such as a powder. The powder is held in image areas by the electrostatic charges on the layer. Where the charge field is greatest, the greatest amount of powder is deposited; where the charge field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the document or object being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably affixed thereto to form a permanent print.

One typical device for fixing the toner particles to the backing sheet is by a heated pressure fuser roll system in which the copy sheet is passed through the nip of a Teflon coated heated fuser roll and a backup roll as described in US. Pat. Nos. 3,256,002 and 3,268,351. In such fusing systems, care must be taken to remove unwanted toner particles from the heated fuser roll prior to its contact with the copy being fused. If care is not taken to keep the fuser roll free of toner particles, these toner particles can build up on the face of the fuser roll and degrade the quality of the fix by removing the fusing properties on the surface of the roll contacting the copy sheet and toner images. Furthermore, such unwanted toner particles can be released from the fusing roll upon its subsequent contact with the image to fuse toner particles to the copy sheet in non-imaged areas. A wick is generally used to dispense silicone oil by gravity on the external Teflon surface of the heated fuser roll by a pad overlying the heated fuser roll.

While the gravity dispensing wick in pad form is satisfactory where the wick is elevated over the nip it is not altogether satisfactory in other arrangements such as where the heated fuser roll is dispensed as the bottom roll of the fusing system.

It is therefore an object of the present invention to improve heated pressure fusing systems.

It is another object of the present invention to improve lubricating wick assemblies of high temperature stability for use with heated pressure fusing systems.

It is another object of the invention to provide wicking assemblies capable of retaining oil over a long shutdown period against gravity.

It is still another object of the present invention to enhance the wicking properties of an oil dispensing wick.

lt is still another object of the present invention to provide an improved oil wicking assembly which is 7 compatible with silicone oil and conforms to objects.

It is still another object of the invention to provide an oil wicking assembly which has a main wick and an auxiliary wick to dispense sufficient oil to the main wick in the event that the main wick applicator is inoperative.

It is still another object of the present invention to minimize unnecessary maintenance of copier/duplicator systems.

These and other objects of the instant invention are obtained by a new and improved lubricating wickassembly which comprises a main wick which contacts the heated fuser roll and an applicator roll and an auxiliary wick having one extremity below the oil supply level and the other extremity in contact with the applicator roll and the main wick.

Further objects of this invention together with additional features and advantages thereof will become apparent from the following detailed description of the embodiment of the invention when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic representation of an automatic xerographic reproducing machine incorporating a heated pressure fusing system utilizing the improved oil dispensing apparatus of the present invention;

FIG. 2 is a side elevational view of the heated pressure fusing system according to the present invention;

FIG. 3 is an isometric view of the wicking assembly; and

FIG. 4 is an exploded view of the substantially smooth fuzz-free lower surface of the wicking assembly.

Referring now to the drawings as shown in FIG. 1 an embodiment of the invention in a suitable environment such as an automatic xerographic reproducing machine. The automatic xerographic reproducing machine includes a xerographic plate or surface 10 formed in the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing joumaled in a frame to rotate in a direction indicated by the arrow. The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations.

For purposes of the present disclosure the several xerographic processing stations in the path of movement of the plate surface may be described functionally as follows:

a charging station A which the uniform electrostatic charge is deposited onto the photoconductive plate;

an exposure station B at which light or radiation pattern of copies to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copies to be reproduced;

a developing station C at which xerographic developing material including toner particles have an electrostatic charge opposite to that of the latent electrostatic image is cascaded over the latent electrostatic image to form a powdered image in configuration of the copy being reproduced;

a transfer station D which the powdered image is electrostatically transferred from the plate surface to a transfer material such as paper which is then passed through heated pressure fusing system according to the present invention as will be described hereinafter; and

a drum cleaning and discharge station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and at which the plate is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

For further details of the xerographic processing stations reference is made to copending application Ser. No. 838,902 filed July 3, i969.

Referring now in particular to FIG. 2 there is shown the heated pressure fusing system of the present invention which includes a heated fuser roll 16 and a backup pressure roll 18. Fuser roll 16 is a hollow circular cylinder with a metallic core 20 and a Teflon layer 22. A lamp 24 serves as a source of thermal energy and is located at the center of the fuser roll. Power to the lamp is controlled by a thermal sensor generally called a thennistor contacting the periphery of the fuser roll as described for example in U.S. Pat. No. 3,357,249. The backup roll 18 is also a circular cylinder and is made up of a metal core 30 surrounded by a thick rubber layer 32 and also a Teflon layer 34 to prevent soaking silicone oil into rubber layer 32 and subsequent swelling.

When the two rollers 16 and 18 are engaged as shown in FIG. 2 the applied load deforms the rubber in the pressure roll to provide the nip with a finite width. The copy sheet 40 electrostatically bearing the toner images 42 on the other side thereof is brought into contact with the nip of the rolls with the toner image contacting the fuser roll 16. For a given temperature of the fuser roll, the fusing rate will depend upon the contact arc length of the support material against the dwell time, i.e. the time the toner image remains between the fuser roll 16 and the backup roll 18. Dwell time can be varied either by changing the surface velocity of the rolls or by varying the contact arc length and holding the speed of the roll the same. Contact arc length depends on the softness of the rubber on backup roll 18 and on the amount of pressure between the rolls l6 and 18. The mechanism for driving the rolls for lowering and raising the rolls into contact can be accomplished by any suitable means as that described for example in U.S. Pat. No. 3,291,466 or by a suitable mechanical camming device.

As a sheet of material is advanced between the rolls 16 and 18 the toner image on thesupport material will contact the peripheral heated surface of the roll 16 whereby the toner image becomes tackified and in this tackified condition the toner will tend to offset on this roll except that it is partially prevented from doing so by the Teflon coating on the roll. It is by the lubricating wick assembly of the present which is used to apply a thin film of offsetting preventing liquid such as silicone oil to the Teflon surface 22 of the fuser roll 16 that offset is prevented.

An oil applicator apparatus 45 includes lubricating wick assembly 48, an oil pan 50 for maintaining a supply of silicone oil 51 and an applicator roll 52. The oil pan is loaded against the fuser roll by a spring action mounting not described as details of the mounting form no part of the present invention. Applicator roll 52 is used to convey a thin film of oil to the bottom face 55 of the lubricating wick assembly as the applicator roll is rotated in the direction shown by the arrow. Desirably,

the applicator roll 52 is driven by an oil dispenser motor 58 which is energized during the fusing operation depending upon the number of copies being produced. In accordance with the present invention lubricating wick assembly 48 includes two different layers of wicking materials. One layer 62 is Teflon which contacts the surface of the fuser roll 16. Another layer 64 is made of Nomex which has its underside S5 in contact with the applicator roll 52. Both Teflon and Nomex are trademarks of DuPont Co. of Wilmington, Delaware. Layers 62 and 64 are assembled in overlapping relationship and their ends are clamped between plates 66 and 68 which are secured by any suitable means such as screws 70 as best shown in FIG. 3. Spring metal brackets 72 and 74 serve to provide support and conforming characteristics to the fuser roll for the assembly. Tab portions 76 are provided for facilitating the handling of the lubricating wick as sembly for insertion and removal of the assembly into and out of the fuser system. Teflon is used as the upper layer because it has high lubricating characteristics as well as thermal stability at elevated temperatures ranging up to 400F and above. Nomex is used as the lower layer because of the thermal stability at elevated temperatures up to 400F and above and due to its high oil retention characteristics.

In order to enhance the oil retention characteristics and also enable trouble free application of oil to the surface of the Nomex layer 64, the lower surface 55 is flame treated to burn all the loose fibers to render a reticulated pattern free of loose fibers as best shown in FIG. 4. Burning should be sufficient to form the surface fibers into a porous membrane or a finished pattern. It has been found that removal of these fibers from the Nomex layer has enabled a high oil retention of the layer while insuring that the applicator roll does not stall which is normally the case where the layer is dry which is caused by oil leaking through loose fiber material. Since the applicator roll motor is desirably of a low power unit it is essential that there be no binding between the Nomex layer and the applicator roll causing the motor to stall. It has been observed that with the fuzz and/or loose fibers removed that motor stalling is prevented and high oil retention qualities retained.

In accordance with the present invention, the oil dispensing apparatus utilizes an auxiliary wick which may be made out of any suitable wicking material. Suitable materials are Corfam, Nomex and Dacron. Preferably the auxiliary wick material will be able to withstand high temperatures, as high as 400F. The auxiliary wick is arranged so that it is touching the applicator roll in close proximity to the main wick. The auxiliary wick is maintained in position by support member 77 which is made of any suitable thermally conductive material and is secured in place by a holding member 80 supported on the bottom of the oil pan.

It should be understood that the auxiliary wick may contact the main wick or be closely spaced as desired. Support bracket 77 preferably is made of any suitable thermally conductive material such as metal in order to enhance the transfer of oil from the auxiliary wick to the applicator roll. It has been found that a temperature gradient may exist between the auxiliary wick and the applicator roll and hence a thermally conductive support member serves to minimize this temperature gradient. The auxiliary wick 75 serves to bring the oil up to the applicator roll to a level such that upon rotation of the roll during one-half of one copy time the oil contacts the wick assembly. It has been found that the auxiliary wick is useful especially during a short run operation when rotation of the applicator roll is small and the oil to the wick assembly must be supplemented to equalize the differential supplied during a much longer run. Thus, in the case of a long run, the oil will be primarily supplied by the applicator roll due to a lag in the capillary action of the auxiliary wick. But during a single or shorter run, the oil dispensing level is increased due to oil coated onto the top of the applicator roll surface by the auxiliary wick.

By the above invention it has been found that the auxiliary wick not only provides the advantages described above but additionally minimizes any variation in the oil film being dispensed due to changes in the oil level in the oil pan. Specifically, due to the configuration of the auxiliary wick arranged around the applicator roll, a uniform amount of oil is continuously supplied to the heater fused roll irrespective of changes in the oil level.

While the instant invention as to its object and advantages has been described as being carried in a specific embodiment thereof it is not intended to be limited thereby but it is intended to be covered broadly 1. In a heated pressure roll fusing system for fusing toner images produced by an electrostatic copying machine in which a heated fuser roll disposed below the copy path is coated with an oil to prevent toner oft set, an improved oil dispensing apparatus comprising an applicator roll mounted for rotation in the oil for dispensing oil onto the lower surface of a wicking assembly where copies are being processed,

a wicking assembly including main wick means positioned between the applicator roll and a heated fuser roll and auxiliary wick means,

said auxiliary wick means arranged on applicator roll surface and extending from below the oil level to a location in close proximity to the main wick means.

2. Apparatus according to claim 1 wherein one end of said auxiliary wick is maintained at the bottom of the oil supply by a holding member.

3. Apparatus according to claim 2 wherein said auxiliary wick means is supported in overlying contact with said applicator roll by a thermally conductive support member.

4. Apparatus according to claim 3 wherein said auxiliary wick is made of a material from the group consisting of Dacron, Nomex and Corfam.

5. Apparatus according to claim 1 wherein the lower surface of the wicking assembly is a substantially smooth membrane-like fuzz-free area. 

1. In a heated pressure roll fusing system for fusing toner images produced by an electrostatic copying machine in which a heated fuser roll disposed below the copy path is coated with an oil to prevent toner offset, an improved oil dispensing apparatus comprising an applicator roll mounted for rotation in the oil for dispensing oil onto the lower surface of a wicking assembly where copies are being processed, a wicking assembly including main wick means positioned between the applicator roll and a heated fuser roll and auxiliary wick means, said auxiliary wick means arranged on applicator roll surface and extending from below the oil level to a location in close proximity to the main wick means.
 2. Apparatus according to claim 1 wherein one end of said auxiliary wick is maintained at the bottom of the oil supply by a holding member.
 3. Apparatus according to claim 2 wherein said auxiliary wick means is supported in overlying contact with said applicator roll by a thermally conductive support member.
 4. Apparatus according to claim 3 wherein said auxiliary wick is made of a material from the group consisting of Dacron, Nomex and Corfam.
 5. Apparatus according to claim 1 wherein the lower surface of the wicking assembly is a substantially smooth membrane-like fuzz-free area. 